In known conventional methods for arraying ferritin or inorganic particles contained in ferritin on a solid, arraying is carried out by way of electrostatic interaction on a pattern having electrostatically reversed polarity produced by a lithography technique (for example, see NPL 5).
NPL 5 discloses: applying a resist on a silicon oxide substrate; developing the resist in areas exposed with electron beam lithography to remove the resist; exposing the areas on which the silicon oxide substrate was exposed to a vapor of a silane coupling agent having an amino group attached to the end, specifically, vapor of aminopropyltrimethoxysilane, so as to allow an amino-terminal silane coupling agent to be adsorbed only to the exposed areas; and then removing the resist with a solvent to form a pattern by amino-terminal silane coupling on a part of the silicon oxide substrate, in which arraying ferritin only on an amino-terminal silane coupling-modified pattern is enabled by controlling electrostatic interaction by adjusting the pH and the ionic strength.
A method in which modification of a ferritin surface with a peptide consisting of six amino acids (arginine-lysine-leucine-proline-aspartic acid-alanine: hereinafter, denoted as RKLPDA in terms of one letter code) selected so as to provide an affinity to titanium (see NPL 1) imparts to ferritin an affinity to titanium, and further interaction with the solid surface is weakened using a nonionic surfactant to permit selective array on a titanium pattern (see PTL 1, and NPL 3) is also known.
NPL 4 discloses an increase in selection ratio resulting from the difference of amounts of adsorption of the nonionic surfactant in selective array on titanium by way of the peptide RKLPDA. NPL 4 discloses that a larger amount of the nonionic surfactant is adsorbed on hydrophobic substrates and silicon substrates as compared with titanium substrates. NPL 4 suggests that a large amount of nonionic surfactant would be adsorbed as long as the substrate is hydrophobic. However, NPL 4 fails to disclose any mechanism of occurrence of the difference of adsorption on the hydrophilic substrate, titanium, and on silicon.
On the other hand, PTL 2 discloses a method of selective arraying ferritin on titanium or silicon nitride on platinum or silicon oxide by way of only the difference of amounts of adsorption of a nonionic surfactant. Materials which may be an affinity target of the peptide RKLPDA are disclosed in NPL 2. NPL 2 discloses that the peptide RKLPDA has affinities to titanium, silicon, and silver, whereas it does not have affinities to gold, chromium, platinum, tin, zinc, copper, and iron.
In brief, it has been known so far that nonionic surfactants have an effect of weakening the interaction between a protein and a substrate, the difference of amounts of adsorption on a solid surface enables protein array on hydrophobic surfaces such as gold and platinum as well as on silicon oxide surface to be selectively inhibited, and that modification of a protein surface with a peptide RKLPDA enables affinities to titanium, silicon and silver to be imparted.